The present invention relates to a compressor that is driven by a power source (a vehicle engine), and in particular, to a vehicle air-conditioner compressor with an integral control unit.
As described in Japanese unexamined patent publication No. 2001-7341, a typical vehicle air-conditioner includes a compressor, a condenser, a decompressor, an evaporator, and an AECU (air-conditioner electronic control unit) for controlling an electromagnetic clutch, which engages and disengages the compressor, a variable capacity mechanism, cabin units installed in the passenger compartment, such as an air mix door and a blower mode door, and the like. The AECU controls the operation of the compressor on the basis of the air-conditioning heat load (i.e., the refrigerating capacity of the evaporator, which can be determined by the actual temperature of the passenger compartment or by a temperature selected by the vehicle's occupants).
Despite the fact that the air conditioner (i.e., the compressor) is driven by the engine, generally, the AECU does not take into account the vehicle-running state (i.e., the load on the engine). That is, generally, air conditioners (compressors) are controlled on the basis of the air-conditioning load.
However, the air conditioner (the compressor) consumes the most power of the accessories driven by the engine. Therefore, the variations in the load of the air conditioner (the compressor) have a great influence on the performance of the vehicle.
On the other hand, it has been proposed to perform variable control of the compressor (a discharge volume control or control of the time of engagement of the electromagnetic clutch) in response to a request from an EECU (engine electronic control unit), which controls the engine. In this case, however, since the compressor is controlled by the AECU, the EECU is forced to generate a command for changing (curtailing) the output of the compressor to the AECU.
For the AECU, however, the request from the EECU is provided as an interruption request and is not included in a routine typically performed for air-conditioning control, so that such a request from the EECU will be handled after completing the typical air-conditioning control routine. Thus, the request from the EECU cannot be quickly handled.
In general, furthermore, the air conditioner has a pressure sensor on the output side of the condenser for detecting the pressure of the refrigerant to make a judgment as to whether the driving torque of the compressor is appropriate and whether an abnormality has occurred in the air conditioner (i.e., whether the pressure on the high-pressure side is abnormally high). Therefore, there is a need to consider the pressure loss in the condenser. In other words, the pressure loss to be considered is different for each kind of vehicle. Thus, it has been difficult to decrease the number of steps in the process for developing the air conditioner.